1. Field of the Invention
The invention relates to disk drive actuator assemblies and, more particularly, to aerodynamic actuator latching mechanisms and air guides therefor.
2. Description of the Prior Art
Data storage devices employing rotating magnetic media disks are known for high capacity, low cost storage of digital data. Such disks typically contain a multiplicity of concentric data track locations, each capable of storing useful information. An actuator assembly facilitates access of the information by selectively positioning a transducer head over a selected data track. The actuator assembly typically contains a transducer head assembly containing the transducer head, a carriage assembly, and a driving mechanism.
More specifically, the transducer head assembly contains at least one magnetic head attached to a slider and the slider is, in turn, attached to a load beam that biases the slider toward the surface of the disk. The carriage assembly supports, at one end, the load beam of the transducer head assembly. At another end of the carriage assembly is an actuator motor (voice coil motor) that causes the actuator assembly to pivot about a centrally located axis (a stationery shaft) that is positioned adjacent the disk. By selectively energizing the actuator motor, the actuator assembly moves about the shaft and positions the transducer head assembly over the disk surface. Control circuitry controls the actuator motor such that the head assembly is accurately positioned relative to the tracks.
Importantly, the transducer heads are biased by the load beam against the disk surface such that, as the disk is rotating, the slider and heads "fly" on an air bearing above the disk. The spring force of the load beam (referred to herein as a preload force) maintains the heads at a prescribed distance above the rotating disk, e.g., within seven micro-inches. The distance above the disk surface is defined by the rotational velocity of the disk in combination with a specified preload force.
When the disk ceases rotation, the air bearing no longer overcomes the preload force. In most hard disk drives, when power is removed from the spindle motor that rotates the disk, the slider comes to rest upon the disk surface. To ensure that the slider does not come to rest upon a portion of the disk that contains recorded data, as the disk drive is powered down, the actuator assembly positions the slider over a so-called landing or parking zone on the disk surface. Typically, after power has been disconnected from the disk drive, back-EMF energy from the spindle motor is used, in a well-known manner, to power the actuator assembly and position the transducers in the landing zone. Thus, after the disk ceases to rotate, the transducers have been appropriately positioned for parking and come to rest upon the disk surface in the landing zone.
Conventionally, while the disk drive is not operating, friction between the transducers and the disk surface helps to maintain the actuator assembly in a fixed position. However, lateral mechanical shock to the disk drive can cause the slider and transducer heads to move (slide) radially across the surface of the disk. Such movement, in absence of an air bearing, may result in damage, e.g., abrasions, scratches and dents, to the surface of the disk as well as damage to the slider and transducer heads themselves. Such damage can result in a loss of data and/or transducer malfunction that can render the disk drive inoperable.
Consequently, those skilled in the art have employed a wide variety of actuator latching devices to maintain an actuator assembly in a locked position while the disk is not rotating. When the disk has attained a proper rotational velocity to produce a sufficient air bearing to support the slider, these latching devices release the actuator assembly and permit it to operate through its limited range of travel relative to the disks.
One latching technique of particular relevance to the present invention is an air vane latch. These latches typically contain an air vane latch mechanism that engages, through a spring generated bias force, a moveable portion of an actuator assembly whenever the disk is not rotating. Specifically, the air vane latch contains a rigid air vane extending from or attached to the mechanical latch mechanism. The air vane utilizes the windage from a rotating disk to unlatch the latch mechanism. Specifically, windage from the rotating disk pushes the air vane, creating enough force to overcome the bias force and disengage the latch mechanism from the actuator assembly. One example of an air vane latch is described in commonly assigned U.S. Pat. No. 4,647,997. Other examples of air vane latches are disclosed in U.S. Pat. No. 5,043,834 and 5,036,416. The disclosures of each of these patents are herein incorporated by reference.
However, to produce a sufficient force to overcome the bias force, such air vane latches require an appropriate air vane size and sufficient airflow within the disk drive enclosure. Accommodating such air vane surface size within a disk drive can require excessive spacing between the disk and disk enclosure. To ensure sufficient windage with a reasonably sized air vane, many disk drives that utilize air vane latches contain multiple disks and multiple air vanes arranged to intercept windage from both surfaces of each disk. Unfortunately, there is typically not sufficient windage to utilize an air vane latch within a disk drive having a single disk. Consequently, to produce sufficient windage in a single disk disk drive, the '997 patent discloses an air vane latch having a plastic air flow generator disk attached to the hub supporting the single storage disk. The air flow generator disk is commonly journalled in a spaced apart parallel relation with the storage disk. The air vane portion of the actuator latch extends between the storage disk and the air flow generator disk. As such, sufficient windage is produced by the rotation of both the storage disk and the air flow generator disk to move the air vane once the disks have attained sufficient velocity to create an air bearing for the transducers. Although the latch mechanism disclosed in the '997 patent functions quite well, the required air flow generator disk necessitates increasing the height dimension of the disk drive to accommodate the air flow generator disk.
Therefore, a need exists in the art for an air-guide within a disk drive enclosure that enables an air vane latch to operate in a disk drive having only a single disk without increasing the dimensions of the disk drive enclosure.